1. Field of the Invention
This invention relates generally to transducers for inducing vibratory signals in an elastic medium such as the earth amd more particularly, to an improved means for coupling the horizontally directed force of a seismic transducer into the earth.
2. Description of the Prior Art
In applicant's co-pending commonly assigned applications, Ser. Nos. 83,070 and 108,206 there are disclosed means for coupling the horizontally directed force of a seismic transducer into the earth consisting of a plurality of downwardly-convergent, wedge-shaped, earth-engaging cleats dependently attached to the transducer support. The horizontal bottom edges of the cleats extend horizontally and are oriented transversely to the direction of transducer motion. In these applications it is disclosed that the cleats may be of differing depth and sharpness, the cleats being preferably configured so that the total edge length of the sharper and deeper cleats is less than that of the blunter and shallower ones to ensure high vertical loading on initial contact with hard surfaces.
The present invention retains all of the advantageous features of the subject matter of the two referenced applications but seeks to further extend the versatility of these designs.
It is therefore a general object of this invention to provide an improved means of coupling the horizontally directed force of a transducer into an elastic medium such as the earth.
It is a further object of this invention to provide means for coupling the horizontally directed force of a transducer into the earth which improves penetration in and coupling to hard rock surfaces.
It is yet another object of this invention to provide means for coupling the horizontally directed force of a transducer into the earth by means which are well adapted both for field modification and for replacement of damaged or worn parts.
Other and further objects and advantages of the invention will become apparent upon consideration of the following detailed description and drawings.
In summary, in accordance with the preferred embodiment of the present invention means are provided for coupling the energy of a horizontal vibrator into the earth comprising a plurality of downwardly-convergent, earth-engaging cleats dependently supported from said transducer. The cleats are in the form of inverted wedges each having a pair of lateral load-bearing faces converging to form a horizontal cleat edge extending transversely to the direction of transducer motion. A plurality of downwardly-projecting teeth are affixed to the horizontal edges of at least some of such cleats. In one embodiment the teeth are mounted on or form a part of replaceable cleat inserts. The teeth are narrow in relation to the total edge length of the cleats. The resultant high loading on these teeth due to the hold-down weight of the transducer enables instant penetration and good coupling of the transducer even on extremely hard rock surfaces.